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Last update: September 2, 2022

15 Best Fish For Small Tanks (With Pics!)

In a 2018 study, Marchio EA determined that keeping a freshwater aquarium resulted in an increased conservation ethic.

Fish keeping is becoming increasingly popular among young children and adults alike. Those who take up the hobby seem to be hooked as they bring their love for fish into adulthood.

And part of that journey is ensuring you understand the requirements of different fish for small tanks.

Conducting significant research on the subject before purchasing a tank and accessories is, naturally, highly recommended.

If you’re a beginner, we recommend beginning with freshwater fish would be prudent as the setup is less expensive, and freshwater fish are easier to keep.

Let’s go over some of the fish you can get for your small tank and the requirements you have to fulfill to ensure they have a healthy and long life.

Fancy Guppies

Fancy Guppies

Aquarists favor Fancy guppies as one of the best fish for small tanks because of their hardiness and low price.

Moreover, they come in multitudes of magnificent colors and patterns, making for an eye-catching tank. Since guppies are tropical fish, they prefer a warm, alkaline environment with fresh water.

It’s a good idea to learn to differentiate between males and females, as they are prolific breeders, which can lead to an overabundance in your tank.

  • Water Temperature: 74 – 82° F
  • Tank Size:
    • >5 gallons for 3 fish
    • >10 – 20 gallons to allow for breeding
  • Alkalinity pH: 6.8 – 7.8
  • Water Hardness: <10 dGH
  • Length: 1 ½ – 2 inches
  • Food Preferences: Omnivore: algae, mosquito lava, flake food
  • Lifespan: ± 2 years
  • Originates: North-east, South America

Zebra Danio

Zebra Danio

Danios are a part of the minnow family and are freshwater fish that thrive in ponds. They’ll flourish in your tank with just a little effort since they are quick-breeding.

Unlike the vertical stripes of a zebra, horizontal blue stripes run along this sleek fish’s body, breaking the silver coloring.

  • Water Temperature: 70 – 78 °F
  • Tank Size: >5 gallons for 5 – 6 fish (preferably 25 gallons)
  • Alkalinity pH: 7.0 – 7.8
  • Water Hardness: 4 – 15 dGH
  • Length: 3 inches
  • Food Preferences: Omnivore: almost anything
  • Lifespan: 3.5 – 5.5 years
  • Originates: Southern Asia

Neon Tetra

Neon Tetra

Neon tetras are easy to keep and stunningly pretty, making them attractive fish for small tanks. Their bodies are a mix of silver and gold, and, like Zebra Danios, they are sleek and long.

A metallic blue stripe runs across the top of the Neon Tetra from tip to tail. And a bright red ribbon runs horizontally along the back half of the body. This fish is most at home in warm waters.

  • Water Temperature: 72 – 76 °F
  • Tank Size: >10 gallons for 6+ fish
  • Alkalinity pH: 6.0 – 7.0
  • Water Hardness: <10 dGH
  • Length: 2 ½ inches
  • Food Preferences: Omnivore: flake food, shrimps
  • Lifespan: 8 – 10 years
  • Originates: Southeast Columbia, Eastern Peru

White Cloud Mountain Minnow

White Cloud Mountain Minnow

The white cloud mountain minnow is distinguishable by its red-tipped nose, tail or caudal fins, red-tipped dorsal fins, and white-tipped ventral fins.

Their silver scales shimmer with green or bright pink, and one or two horizontal black lines run along their bodies.

The white cloud mountain minnow requires cooler water than others, so take heed of that when considering compatible fish for small tanks.

  • Water Temperature: 60 – 72 °F
  • Tank Size: >10 – 12 gallons
  • Alkalinity pH: 6.0 – 8.0
  • Water Hardness: 5 – 19 dGH
  • Length: 1 ½ inches
  • Food Preferences: Opportunistic Omnivore: mostly frozen blood worms, mosquito larvae, shrimp
  • Lifespan: 5 years+
  • Originates: China

Harlequin Rasbora

Harlequin Rasbora

The primary two colors of a Harlequin Rasbora are orange, pink, or variations thereof, with a solid black triangle marking the back half.

This unusual coloring gives it the beautiful appearance of a clown or harlequin. These omnivorous fish are easy to maintain, making them a good choice for small tanks. 

  • Water Temperature: 73 – 82 °F
  • Tank Size: >10 gallons
  • Alkalinity pH: 6.0 – 7.8
  • Water Hardness: <12 dGH
  • Length: 1.75 up to 2.0 inches
  • Food Preferences: Omnivore: prefer live food; flake food
  • Lifespan: 5 – 8 years
  • Originates: Singapore Sumatra, Malaysia, Southern Thailand

Dwarf Gourami

Dwarf Gourami

Dwarf Gourami males have unusual diagonal lines, alternating between blue and red. The female is less spectacular, though her glossy silver coloring is still striking.

A dark blue stripe runs from head to tail at the base of the dorsal fin. They’re indeed a beautiful species to add to your small tank but keep in mind that they require a fair amount of well-vegetated space to swim in.

  • Water Temperature: 72 – 82 °F
  • Tank Size: >15 gallons + for 2 fish
  • Alkalinity pH: 6.0 – 7.5
  • Water Hardness: 4 – 10 dGH
  • Length: 3.5 inches
  • Food Preferences: Omnivore: small insects larvae, algae-based flake food
  • Lifespan: 4 – 6 years
  • Originates: Assam, India, Bangladesh, West Bengal

Betta Fish

Betta Fish

The Betta Fish, or Siamese fighting fish, are more susceptible to disease in cool water. They need warm water, so you must absolutely get them a water heater.

Their colors and tail shapes vary, and a labyrinth organ allows them to take in surface air, so they can survive in low-oxygen waters.

This aggressive male would be fairly safe to keep with fast-swimming species, but perhaps they’re not the best choice of fish for small tanks.

Keep activity outside the tank down, and keep in mind that they dislike too much sun or breeze. 

  • Water Temperature: 75 – 80 °F
  • Tank Size: >3 gallons
  • Alkalinity pH: 6.8 – 7.5
  • Water Hardness: 5 – 20 dGH
  • Length: 2 4 – 3.1 inches
  • Food Preferences: Carnivores: prefer live crustaceans, insects; frozen blood worms
  • Lifespan: 2 – 5 years
  • Originates: Southeast Asia

Chili Rasbora

Chili Rasbora

The sleek and beautiful red and black coloring of the Chili Rasbora makes them a favorite among Aquarists.

If you’re considering them for your small tank, keep in mind that they prefer an acidic water pH. 

The color of the Chili Rasbora ranges from cherry-red to blood red, and their solid or split black lateral lines have a shimmering appearance.

Also, their fins have patches that match the red coloring. With a low water hardness tolerance, they’re most comfortable in swamps. 

  • Water Temperature: 68 – 82.4 °F
  • Tank Size: >5 gallons
  • Alkalinity pH: 4.0 – 7.0 (acidic)
  • Water Hardness: 1 – 6 dGH
  • Length: 0.6 to 0.8 inches
  • Food Preferences: Carnivore: blood worms, chopped micro worms
  • Lifespan: 4 – 5 years
  • Originates: South West Borneo, Indonesia

Bluefin Notho

Bluefin Notho

Also called the rachovii killifish, the extremely bright coloring of the males makes them attractive fish for small tanks.

Their scales comprise alternating red and blue vertical lines, while their tails and fins are black and blue. Interestingly, locals refer to them as Rain Fish, as their eggs evaporate under the hot African sun, and live fish come down with the rain.

  • Water Temperature: 68.0 – 75.0 °F
  • Tank Size: 10 – 15 gallons
  • Alkalinity pH: 6.0 – 7.0
  • Water Hardness: 5 – 20 dGH
  • Length: 2.4 inches
  • Food Preferences: Carnivore: live mosquito larvae, brine, shrimp; frozen blood worms
  • Lifespan: 1 – 1 ½ years
  • Originates: Mozambique

Celestial Pearl Danio

Celestial Pearl Danio

Also known as Galaxy Rasbora, this peaceful species is closely related to the Danio. They choose lifetime mates and don’t observe specific breeding seasons.

Their name is derived from the pink, blue, or violet, pearl coloring of their scales.

A red or orange line runs along their abdomen, taking about 1 ⅓ of their bodies. Their unusual patterning makes them a striking fish for small tanks.

  • Water Temperature: 73 – 79 °F
  • Tank Size: >10 gallons
  • Alkalinity pH: 6.5 – 8.4
  • Water Hardness: 2 – 10 dGH
  • Length: ± 1 inch
  • Food Preferences: Carnivore: prefer live baby shrimps, krill, white worms
  • Lifespan: 3 – 5 years
  • Originates: Hopong, east of Inle Lake, China

Sparkling Gourami

Sparkling Gourami

This little guy is like a brightly lit, science-fiction, alien underwater craft. Like the Betta Fish, they have a labyrinth organ that enables them to take in surface oxygen.

These fish veer away from conflict, so they’re an excellent choice for small tanks as they live harmoniously in communities.

  • Water Temperature: 75 – 77 °F
  • Tank Size: >10 – 15 gallons
  • Alkalinity pH: 5.5 – 7.0
  • Water Hardness: 5 – 16 dGH
  • Length: 1.5 inches
  • Food Preferences: Omnivore: prefer live food; frozen blood worms
  • Lifespan: 4 – 5 years
  • Originates: Southeast Asia

Otocinclus

Otocinclus

Part of the catfish family, this small fish prefers neutral to slightly acidic water.

While they sometimes clean algae from the glass of your tank, they like to clean the particles off plants, making them essential fish for small tanks.

There are 22 species of Otocinclus, most of which are golden brown and dark brown, with a dark brown line running horizontally along the center of the body. 

  • Water Temperature: 72 – 79 °F
  • Tank Size: >10 gallons for 6+ fish
  • Alkalinity pH: 6.7 – 0.5
  • Water Hardness: 7 – 15 dGH
  • Length: 1 ½ – 2 inches
  • Food Preferences: Omnivore: algae-based flake foods, frozen blood worms
  • Lifespan: 5 – 7 years
  • Originates: South America

Cardinal Tetra

Cardinal Tetra

The Cardinal Tetra thrives best in natural pH waters. Their three-tiered coloring makes them spectacular fish for small tanks.

They have electric sky-blue crowns on their head and drapes that run from the front to near the start of the tail.

Beneath that, a broad band of red tips the tail and runs almost the full length of the body. They also have a small whitish area.

  • Water Temperature: 73 – 81 °F
  • Tank Size: >10 gallons for 5+ fish
  • Alkalinity pH: 2.8 – 8.8
  • Water Hardness: <4 – dGH
  • Length: 1 ¼ inches
  • Food Preferences: Omnivore: small crustaceans and worms; 3/4 pellets or flakes
  • Lifespan: ± 5 years
  • Originates: Venezuela, Brazil, Colombia

Pygmy Corydoras

Pygmy Corydoras

Like the Otocinclus, the Pygmy Corydoras are a small breed of catfish with metallic silver scales.

A prominent black line runs horizontally mid-body, dissecting the metallic silver scales, from the tip of their nose to the start of the tail—which splits in 2.

They swim in groups around mid-tank. Since they are bottom and mid-tank swimmers, they are perfectly suitable for small tanks.

  • Water Temperature: 72 – 79 °F
  • Tank Size: >10 gallons for 4 – 8 fish
  • Alkalinity pH: 6.4 – 7.4
  • Water Hardness: 2 – 15 dGH
  • Length: 1 ⅓ inches
  • Food Preferences: Omnivore: frozen blood worms, mosquito larvae, catfish pellets
  • Lifespan: ± 3 years
  • Originates: Inland South America (now, Madeira River basin in Brazil)

Endler’s Livebearer

Endler’s Livebearer

If you go for the Endler’s Livebearer fish, you should know that it’s best to keep a 1:1 ratio of males to females.

Don’t go for a higher male count as males can stress the females, sometimes even to their deaths. Evolutionary biologist, Dr. John Endler, rediscovered this fish when it was thought to be extinct.

It comes in a multitude of bright variants, especially the males, while the female has a slightly silver-ish hue.

  • Water Temperature: 72 – 82 °F
  • Tank Size: >5 – 10 gallons for 3 fish (2 females to 1 male)
  • Alkalinity pH: 7.0 – 8.5
  • Water Hardness: 12 – 20 dGH
  • Length: 1.8 inches
  • Food Preferences: Omnivore / Herbivore: insects and algae-based flakes
  • Lifespan: 2 – 3 years
  • Originates: Buena Vista Lagoons, North Eastern Venezuela; Campoma
  • Feel free to rearrange them as you see best fit for the flow of the article. 
  • Put the common name, scientific name, difficulty level, life span & adult size on each review.

Important Things to Remember – Small Fish Edition

Important Things to Remember - Small Fish Edition

Nano fish are fish for small tanks of around 10 gallons, and they grow to less than 2 ½ inches.

While some fish in this list are not specifically nano fish, they can be kept with smaller fish, as long as you consider your tank size. 

It’s wise to steer clear of the more aggressive fish or ensure your non-aggressive fish are fast swimmers.

And keep a good amount of foliage and tank decorations, such as rocks and driftwood.

Move these and the filter positioning around since the aggressive breeds are territorial, and ‘environment’ changes make them less so. 

Water hardness is another thing to consider when getting fish for your tank. This is determined by different chemicals in the water and influences the water pH levels.

Water hardness affects the salt concentration and calcium levels in the fish’s blood. Therefore, if it’s incorrect for the species, their cells could either dry up or burst from over-filling.

You can read more about osmoregulation to discover the importance of maintaining salt and water balance in your aquarium.

Generally, cold-water fish for small tanks need a pH of 7.0 – 7.5 and a hardness of 150 dGH, Tetras require a pH of 6.5 – 7.0 and a water hardness of 50 – 100 dGH, and Livebearers prefer a pH of 7.0 – 7.5 with a water hardness of 250 – 300 dGH.

Ensure your tank’s pH, and dGH levels are the right for the fish you want.

In addition to ensuring you’ve prepared the proper water for your fish, you have to make sure you put compatible species together in the tank. 

If you go through the list of fish we have included, you’ll get a good idea of which fish you can match together.

To sum up, these are the factors you must consider when taking care of small fish in small tanks. 

  • Alkaline vs Acidic pH Requirement
  • Water Temperature Requirement
  • Water Hardness Requirement
  • Tank Size Requirement
  • Avoiding Aggressive Species

Small Tank Maintenance and Setup

Small Tank Maintenance and Setup

While many species can adapt to different water pH levels, there are other tank-related preparations that you have to consider.

After all, you are creating an artificial environment far from their natural habitat. 

You may have heard how, but there’s a thing called “The New Tank Syndrome” – you did everything by the book, but all your fish die within the first weeks.

It’s downright disheartening and can even make you think that fish-keeping isn’t for you. However, there is hope.

Many believe this happens when the tank’s nitrite and alkaline levels get too high, usually coming from undigested food and fish waste. Ammonia damages gills and affects the brain.

Remember – nitrifying bacteria can manage this waste. This process is called the nitrogen cycle, and it takes about a month to establish. 

There are things you can do to move the process along, though. Add gravel from an existing aquarium, thereby introducing the bacteria.

Some commercial products contain these bacteria, so you could add those as well. Live plants can stabilize the ammonia levels as they absorb it. Start with 10% of the tank’s capacity, and select the hardiest fish.

For the initial weeks, feed small quantities every second day. Regularly test the ammonia nitrite levels. If these get too high, do small water changes at a time until the levels are correct. 

Ensure always to keep the water temperature consistent. You may need a correctly sized heater for the winter months.

Keep your tank out of drafts, and slowly change the water when cleaning the tank. 

When cleaning a populated fish tank, never remove the fish or replace over 50% of the water. This will kill the essential bacteria and, thereby, your fish.

Also, when you do, never use any detergent on them at all. Instead, soak them in warm water. You won’t need to clean your plants or decorations until they look dirty.

  • Unplug the heater and filter
  • Scrape algae off the sides
  • Siphon the gravel. 
    • Ensure less than 50% of the water is removed
  • Add new de-chlorinated water to the fish tank.
  • Feel free to combine some of these topics, add your own header sections based on your own research and experience, and rearrange them as you see best fit for the flow of the article.

Conclusion

Before you head out and purchase your new aquarium setup, ensure you conduct proper research and have an idea of what type of fish you want to take care of. Your choice of fish will determine the setup. 

This article talked about freshwater fish, which is perfect for beginners. In fact, it’s not advisable to head into the world of saltwater aquariums until you’ve gained a fair amount of experience with the freshwater counterpart.

In matters of the tank, this article covered pH levels, water hardness, water temperature, tank size, and how to keep your small tank clean.

We also mentioned compatibility, food preferences, and more factors to consider when getting fish for your small tank.

We hope you got all you need and are ready for the responsibility of having an aquarium at home.

Resources:

Ian Sterling

I've been keeping fish for over 30 years and currently have 4 different aquariums – it's an addiction. I'm here to teach you everything there is to know about fishkeeping.

I also use this site as an excuse to spend lots of money on testing and reviewing different aquarium products! You can find my reviews here.

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